More Condor sailings have been scheduled for Thursday 17 February - ahead of the schoolo half-term holidays - because two storms are expected to hit the Channel Islands this weekend.
High-speed services between Friday 18 February and Sunday 20 February have been placed under review as Storms Dudley and Eunice are expected to bring wind speeds of more than 70mph.
Waves could reach more than 5m high.
Passengers on these sailings can transfer to a Thursday sailing for free.
Those services are operating Poole-Guernsey-Jersey-Poole and between Jersey and St Malo.
"The forecast is for really challenging weather patterns in the lead up to the half-term holiday. We want to be prudent and proactive by contacting passengers in advance to notify them that there is significant risk of disruption and to offer them alternatives where possible.
The conditions are unpredictable and may change from the current forecasts, so we continue to assess the situation and will advise travellers over the next 24 to 48 hours of other plans." - Elwyn Dop, Operations Director.
The coastguards in Jersey and Guernsey are urging boat owners to check their moorings ahead of the impending storms.